The present invention relates to a new and improved construction of apparatus for fabricating a plastic insulator equipped with helical-shaped screens or shields, these shields radially protruding from an insulator rod.
At overhead lines for the transmission of voltages greater than 220 kV, for instance in a range of 500 to 700 kV, there are required insulators of several meters length and there arise tensile loads of at least 10 tons. For reasons of fabrication porcelain insulators can only be manufactured with a length of maximum about 2 meters. Therefore, for the previously mentioned transmission voltages there are required plastic insulators. These plastic insulators are presently composed of different elements. Typically, for instance, there is employed an insulator rod of desired length as a support element, upon which there is applied, according to different techniques, a protective device against weather or atmospheric conditions which is formed of "TEFLON" or silicon rubber. The insulator rod consists of a glass fiber-synthetic resin mixture. The previously mentioned weather protective device constitutes a protective coating which is provided with a number of shields or screens located along the insulator rod and surrounding the same. These shields therefore radially protrude from the insulator rod and fulfil the purpose of deflecting rain, in order to increase the leakage path along the insulator. As mentioned, the weather protective device and the screens can be applied in different ways to the insulator rod. Thus, it is known to slip over the insulator rod tubular-shaped sleeves containing thereat flange-like mounted screens or shields and to adhesively bond such with the insulator rod. However, each sleeve which is slipped over the insulator rod also can support a number of shields. It is also possible to individually attach the shields or screens at the insulator rod, after such has previously been covered with a protective coating or layer.
The previously mentioned fabrication procedures require a discontinuous manufacturing process. If individual sleeves are used, then they must be fabricated individually or in groups in presses while working at high pressures and temperatures. Plastic insulators of this type are known to the art from French Pat. application No. 2,363,170. An improvement in the plastic insulators can already be obtained if there is realized a continuous manufacturing procedure. Such improved plastic insulator is known to the art from German Pat. No. 1,190,072. Yet, this lastmentioned patent does not disclose how it is possible to economically fabricate such plastic insulator.